Afterburner for internal combustion engine

ABSTRACT

An afterburning system for minimizing hydrocarbon and carbon monoxide, content left unburned in engine exhaust gases of an internal combustion engine. In the afterburning system, an improved afterburning stabilizer is provided including a porous enclosure for uniformly admixing an additional air-fuel mixture, which is burned to form a premixed flame therearound for anchoring the main combustion of the contaminated exhaust gases. A number of projections are mounted upon the porous enclosure for producing small disturbances in the flow of the exhaust gases and for acting as a stable heat source for the main combustion when the premixed flame is formed close to the tips thereof.

United States Patent Maruoka Feb. 20, 1973 54] AFTERBURNER FOR INTERNAL3,042,499 7/1962 Williams ..60/303 COIMBUSTION ENGINE 3,306,035 2/1967Morrell ..60/286 Primary Examiner-Douglas Hart [75] Inventor: HiroyukiMaruoka, Yokohama, Anomey yohn Lezdey Japan [73] Assignee: Nissan MotorCompany Limited, [57] ABSTRACT Yokohama-lapan An afterburning system forminimizing hydrocarbon [22] il Oct 13 7 and carbon monoxide, contentleft unburned in engine exhaust gases of an internal combustion engine.In the PP N 188,959 afterburning system, an improved afterburningstabil- Foreign Application Priority Data izer is provided including aporous enclosure for On. 30, 1970 Japan "/122778 uniformly admixing anadditional air-fuel mixture; which is burned to form a premixed flametherearound for anchoring the main combustion of the [58] 23/277 Ccontaminated exhaust gases. A number of projections are mounted upon theporous enclosure for producing [56] References Cited small disturbancesin the flow of the exhaust gases and 1 I for acting as a stable heatsource for the main com- UNITED STATES PATENTS bustion when the premixedflame is formed close to 2,203,554 6/1940 Uhri ..23 277 c the ups 10Claims, 4 Drawing Figures FI I EXHAUST GASES /I5 SECONDARY Mb Io OFPROPER AIR I6 MIXTURE RATIO I40 CONTAMINATED CLEAN EXHAUST GASES EXHAUSTGASES I8 I8 b 2K3 22 5 ADDITION/ii AIR E I ADDITIONAL 2 I I AIR- FUEL23b {ADDITIONAL IXT RE I I FUEI \k I I9 I? I I 2| I I I 25 SERVO- MOTORCONTROLLER I 2H3 2I CI L Fig. 4

INVENTOR HIROYIM'I Manuela m!n e ATTOR Y SHEET 3 OF 3 RECIRCULA- TIONZONE ZONE 1 l- 9;!jf .I-I L/IIIJAXY/I/I/ OF PROPER MIXTURE RATIO EXHAUSTGASES 3 SMALL TURBULENCES ADDITIONAL AIR- FUEL MIXTURE ADDITIONALAIR-FUEL MIXTURE PAIENTEDFEBZOIQH AFTERBURNER FOR INTERNAL COMBUSTIONENGINE This invention relates to an afterburner for an internalcombustion engine and, more particularly, to an afterburning system forminimizing hydrocarbon and carbon monoxide content left unburned inengine exhaust gases of an internal combustion engine.

Afterburners of the flame type have been used as furnaces that burn outthe small quantities of fuel left unburned in the engine combustionchamber. In order to effect complete combustion of the unburned contentsand therefore to discharge clean exhaust gases, the afterburners of theflame type establish an open flame in the contaminated exhaust gases byadding some amount of extra secondary fuel to the exhaust gases. In thisdirect open flame method, however, there are several concomitantproblems: Since the afterburners are located in an engine exhaust pipethrough which the exhaust gases flow at a high speed, it is quitedifficult to stably maintain or hold the main combustion of the exhaustgases; furthermore, irregular combustions such as misfire or blow-offare often encountered in using the open flame method, thus invitingdeterioration of the main combustion with resultant increased inunburned contaminated emission.

It is therefore an object of this invention to provide an afterburningsystem for an internal combustion engine including an improvedafterburning stabilizer for forming a stable premixed flame to anchorthe afterburning of the contaminated exhaust gases.

Another object of the invention is to provide an improved afterburningstabilizer including a porous enclosure for uniformly admixing anadditional air-fuel mixture supplied thereto and a number of projectionsmounted upon the porous enclosure for producing small turbulences in theflow of the exhaust gases and for acting as a heat source when thepremixed flame is formed closeto the tips thereof.

A further object is to provide a compact afterburning system withreliable ignition performance and without any misfire or blow-off.

In the accompanying drawings:

FIG. 1 is a diagrammatical flow chart of an afterburning system of theinvention;

FIG. 2 is an explanatory view of the overall afterburning system;

FIG.3 is an enlarged sectional view of an embodiment of an afterburningstabilizer and afterburning reactor shown in FIG. 2; and

FIG. 4 is similar to FIG. 3 but shows another embodiment.

Referring now to FIG. 1, an afterburning system of this invention may beprovided with a secondary air supplier 11 for supplying a secondary airto the contaminated engine exhaust gases 12 to produce exhaust gases 13,if desired. The exhaust gases 13 thus obtained are then introduced intoan afterburning or reburning reactor 14 for complete consumption of theunburned content. After reburning the contaminated exhaust gases 12, theafterburning reactor 14 discharges clean exhaust gases 15.

According to a main feature of the invention, the reburning in theafterburning reactor 14 is stabilized by an afterburning stabilizer 16which will be described in detail with reference to FIGS. 2 to 4. Theafterburning stabilizer 16 of the flame type produces a premixed flameacting as a heat source for the reburning of the exhaust gases 13.Additional air-fuel mixture is supplied from an additional air-fuelmixture supplier 17 to form and maintain the premixed flame. As shown inFIG. 1, additional air 18 and additional fuel 19 are metered to have aproper mixture ratio and delivered to the additional air-fuel mixturesupplier 17.

In order to effect complete combustion of the exhaust gases 13, thetemperature in the afterburning reactor 14 is maintained at anappropriate level. This temperature control may be accomplished byproviding a mixture flow rate controller 21 which controls the intensityof and therefore thermal energy generated by the premixed flame. Forthis purpose, the mixture flow rate controller 21 regulates flow rate ofthe additional air-fuel mixture 17 which has obtained a proper mixtureratio, in dependence upon the temperature in the afterburning reactor14. The temperature detection is carried out by a temperature sensor 22which may be mounted in the afterburning reactor 14. For initiation ofthe premixed flame, an igniter 23 may be used in the afterburning system10.

More detailed description about the overall afterburning system 10 willbe made with reference to FIG. 2, in which like numerals designate likeelements and parts shown in FIG. 1. In this illustration of anembodiment, the afterburning stabilizer 16 is installed in a reburningchamber 14a defined by a housing 14b of the afterburning reactor 14. Theafterburning stabilizer 16 has a generally spherical shape and islocated upstream of the reburning chamber 14a.

The contaminated exhaust gases 12 are discharged from an internalcombustion engine (not shown) into the reburning chamber 14a. As shown,a metered amount of secondary air 11 may be introduced into thecontaminated exhaust gases 12 by an air injection device (not shown).The introduction of the secondary air 11 may preferably provide apartially admixed exhaust gases of proper mixture ratio falling to thelean side. On the other hand, the additional air 18 is sucked by ablower 18a through a passage 18b, which is vented to the surroundingatmosphere and is in communication with a reservoir 16a of theafterburning stabilizer 16. At the same time, an optimum amount of theadditional fuel 19 is supplied in an atomized condition to the passage18b by a carburetor 19a, which communicates with a fuel pump (notshown).

In operation, the additional air-fuel mixture 17 thus produced isuniformly admixed while passing through a porous enclosure 16b of theafterburning stabilizer 16. Then, the additional air-fuel mixture 17produces the premixed flame when ignited by a spark plug 13a of theigniter 23. This premixed flame is encountered by the flow of theexhaust gases 13. In this instance, the exhaust gases 13 usually containunburned fuel and may also contain the secondary air 1 1, so that theywill easily reburn to consume the unburned fuel content if the reburningchamber 14a is maintained at a high temperature level. The combustionphenomena experienced in the reburning chamber 14a will be discussed indetail with reference to FIG. 3.

In order to control the temperature in the reburning chamber 140, thetemperature sensor 22 senses the temperature level and provides a signalindicative of the temperature level. This signal is introduced into acontroller 21a of the mixture flow rate controller 21. Upon reception ofthe temperature signal, the controller 21a energizes a servo-motor 21bto actuate the same. The servo-motor 21b, which is mechanically coupledwith a throttle valve 210 mounted in the passage 18b, rotates thethrottle valve 21c when actuated. This rotation changes the effectivearea around the throttle valve 210, thus controlling the flow rate ofthe additional air-fuel mixture 17. In this way, the temperature in thereburning chamber 14a is automatically controlled at a predeterminedlevel appropriate for effecting therein complete combustion.

The controller 21a is energized by an energy source 24 through anignition switch 25 and may control the operation of the blower 18a. Thespark plug 23a may also be controlled by the controller 21a throughswitching of a high voltage source 23b.

Turning now to FIG. 3, the afterburning stabilizer 16 further includes anumber of projections 16c mounted upon the porous enclosure 16b. Theseprojections 16c may preferably be made of a heat resistive material andacts as a heat source for the main combustion when the premixed flame isformed therearound. This is because the projections 16c are heated bythe premixed flame and then turns red-hot. In any event, the premixedflame is formed close to the tips of the projections 16c.

As is well known, the exhaust gases 13 is delivered at a relatively highspeed into the reburning chamber 14a. At this instance, the porousenclosure 16b acts as a bluff body establising a wake and arecirculation zone, as shown, downstream thereof. Thus, the porousenclosure 16b as a whole is a flame holder as used in a jet engine. Theprojections 160, on the other hand, produce small turbulences in thestream of the exhaust gases 13. With the premixed flame thus formed, thecombined effects of the small turbulences, wake, recirculation zonestably anchor the main afterburning combustion which is shown as ahatched reaction zone.

In this way, unstable irregular combustions such as a misflre orblow-off, which are otherwise inherent in the conventional afterburningsystem of the flame type, are absolutely eliminated with a resultantcomplete combustion. As an unexpected desirable result, the materialused in the porous enclosure 16b may not have an extremely highheat-resistive property, because the additional air-fuel mixture 17 iscold enough to cool down the enclosure 16b while passing therethrough.Therefore, materials suitable for the porous enclosure 16b are, by wayof example, sintered porcelain and multilayered stainless steel mesh. Onthe other hand, the projections 160 may be made of solid porcelain.

Reference is now to be made to FIG. 4 showing another example of anafterburning stabilizer 16', in which primed numerals indicatecounterparts shown in FIG. 3. In this embodiment, a reburning chamber14a and therefore an afterburning reactor 14 are provided within aporous enclosure 16'b of the afterburning stabilizer 16. A number ofprojections l6'c are mounted upon an inner surface of the porousenclosure l6'b. In this instance, a reservoir l6a is providedsurrounding the porous enclosure 16b.

The additional air-fuel mixture 17 is, in operation, introduced into thereservoir l6a and passes inwardly throughthe porous enclosure 16'b.Then, the mixture 17 is ignited by the spark plug 230 and forms apremixed flame close to the tips of the projections 16"c.

At the same time, the exhaust gases 13 are ignited by lences, wake andrecirculation zone are not expected to a great extentin this embodiment,a uniform high temperature distribution together with stagnantcombustible gases are obtained in the reburning chamber l4'a,respectively because the reburning chamber 14'a is surrounded by thepremixed flame and because the exhaust gases 13 are introduced into thereburning chamber 14a having a relatively large volume. This will leadto reduction of the amount of extra fuel to be added. The reburningchamber 14a is defined by the porous enclosure l6b being cooled, so thatthere will not be a cooling problem of the reburning chamber l4'a.

It should now be appreciated that this invention provides a compactafterburning system for reducing u'nburned content in the engine exhaustgases, with reliable ignition performance and without any misfire orblow-off.

What is claimed is: 1. An afterburning system for minimizing hydrocarbonand carbon monoxide contents left unburned in engine exhaust gases of aninternal combustion engine, comprising:

reburning means having a reburning chamber for reburning the engineexhaust gases therein;

reburning stabilizing means including mixing means having a porousenclosure, and heat source and turbulence producing means having anumber of projections mounted upon said enclosure, for forming apremixed flame close to the tips of said projections to stabilize thereburning of the engine exhaust gases; and

additional air-fuel mixture supplying means for supplying an additionalair-fuel mixture to said reburning stabilizing means,

whereby said porous enclosure uniformly admixes said additional air-fuelmixture while it is passing therethrough, and said projections producesmall turbulences in the flow of the engine exhaust gases and act as aheat source, while heated by said premixed flame, for anchoring thereburning of the engine exhaust gases.

2. An afterburning system according to claim 1, further comprising flowrate control means for controlling flow rate of said additional air-fuelmixture in dependence upon the temperature in said reburning chamber tomaintain said temperature at a predetermined level appropriate foreffecting complete combustion of the engine exhaust gases.

3. An afterburning system according to claim 2, wherein said flowratecontrol means includes a throttle valve rotatably mounted in saidadditional air-fuel mixture supplying means for controlling theeffective area therearound, a servo-motor for rotating said throttlevalve when energized, a controller for controlling energization of saidservo-motor, and a temperature sensor mounted in said reburning chamberfor sensing the temperature therein to control the operation of saidcontroller.

4. An afterburning system according to claim 1, wherein said additionalair-fuel mixture supplying means includes additional air supplying meansfor supplying fresh air to said reburning stabilizing means, andadditional fuel supplying means for supplying an optimum amount ofatomized fuel to the flow of the fresh air.

5. An afterburning system according to claim 4, wherein said additionalair supplying means includes a passage vented to the atmosphere andcommunicating with said reburning stabilizing means, and a blowermounted in said passage for sucking the fresh air into said reburningstabilizing means, and wherein said additional fuel supplying meansincludes a carburetor mounted on said passage.

6. An afterburning system according to claim 1,

wherein said reburning stabilizing means has a generally spherical shapeandis located within and upstream of said reburning chamber.

7. An afterburning system according to claim 6, wherein said projectionsand located externally of said porous enclosure.

8. An afterburning system according to claim 1, wherein the porousenclosure of said reburning stabilizing means defines said reburningchamber.

9. An afterburning system according to claim 8, wherein said projectionsare located internally of said porous enclosure.

10. An afterburning system according to claim 1, further comprisingsecondary air supplying means for supplying secondary air to the engineexhaust gases prior to the reburning operation to provide exhaust gasesof proper mixture ratio.

1. An afterburning system for minimizing hydrocarbon and carbon monoxidecontents left unburned in engine exhaust gases of an internal combustionengine, comprising: reburning means having a reburning chamber forreburning the engine exhaust gases therein; reburning stabilizing meansincluding mixing means having a porous enclosure, and heat source andturbulence producing means having a number of projections mounted uponsaid enclosure, for forming a premixed flame close to the tips of saidprojections to stabilize the reburning of the engine exhaust gases; andadditional air-fuel mixture supplying means for supplying an additionalair-fuel mixture to said reburning stabilizing means, whereby saidporous enclosure uniformly admixes said additional air-fuel mixturewhile it is passing therethrough, and said projections produce smallturbulences in the flow of the engine exhaust gases and act as a heatsource, while heated by said premixed flame, for anchoring the reburningof the engine exhaust gases.
 2. An afterburning system according toclaim 1, further comprising flow rate control means for controlling flowrate of said additional air-fuel mixture in dependence upon thetemperature in said reburning chamber to maintain said temperature at apredetermined level appropriate for effecting complete combustion of theengine exhaust gases.
 3. An afterburning system according to claim 2,wherein said flow rate control means includes a throttle valve rotatablymounted in said additional air-fuel mixture supplying means forcontrolling the effective area therearound, a servo-motor for rotatingsaid throttle valve when energized, a controller for controllingenergization of said servo-motor, and a temperature sensor mounted insaid reburning chamber for sensing the temperature therein to controlthe operation of said controller.
 4. An afterburning system according toclaim 1, wherein said additional air-fuel mixture supplying meansincludes additional air supplying means for supplying fresh air to saidreburning stabilizing means, and additional fuel supplying means forsupplying an optimum amount of atomized fuel to the flow of the freshair.
 5. An afterburning system according to claim 4, wherein saidadditional air supplying means includes a passage vented to theatmosphere and communicating with said reburning stabilizing means, anda blower mounted in said passage for sucking the fresh air into saidreburning stabilizing means, and wherein said additional fuel supplyingmeans includes a carburetor mounted on said passage.
 6. An afterburningsystem according to claim 1, wherein said reburning stabilizing meanshas a generally spherical shape and is located within and upstream ofsaid reburning chamber.
 7. An afterburning system according to claim 6,wherein said projections and located externally of said porousenclosure.
 8. An afterburning system according to claim 1, wherein theporous enclosure of said reburning stabilizing means defines saidreburning chamber.
 9. An afterburning system according to claim 8,wherein said projections are located internally of said porousenclosure.